Rajesh Khanna and Babita were to be introduced with this film.The film was delayed for sometime and Rajesh Khanna made his debut with Aakhri Khat 1966 and Babita with Dus Laakh 1966.
First time Raaz title was used for a Hindi film.Later Many films were made on this title Raaz in1981,Raaz in 2002,Raaz 2 in 2009,Raaz 3D in 2012 and Raaz Reboot in 2016.
The red convertible sports car which Baba - Harindranath Chattopadhyay drives, is old MG Sports 1930 model. The same model car is driven by Dharmendra in the hit movie Yakeen (1969)
In the late 50's, Guru Dutt had launched a film titled,"Raaz". The film starred Sunil Dutt, Waheeda Rehman, Rehman, directed by Shashi Bhushan. After 10 days, Guru Dutt decided to shelved the film. Then in the early 60's, he relaunched another film titled "Raaz" with himself, Waheeda Rehman and Rehman. After shooting 12 reels for unknown reasons,he shelved the film. The movie was based on the novel "The Woman In White". Raj Khosla who was a assistant on Raaz, decided to use the same script and made "Woh Kaun Thi".
The mahurat of the film happened on the sets of Brahmachari.